Current sensors for use in the measurement of current in a conductor are well known. Such current sensors are commonly used in troubleshooting and control applications. For example, it may be important to know how much current is flowing through a wire that drives a motor in order to verify that the motor is operating properly.
AC current sensors do not typically require that a circuit be broken in order to make a current measurement. AC current sensors typical comprise inductive elements into which current is induced by the changing magnetic field surrounding an AC current conductor. However, DC current is not suitable for inducing current into an inductive element in this manner.
DC current measurement devices that required that a circuit be broken in order to make a measurement are common. For example, moving coil current meters (galvanometers) are used by breaking a circuit and inserting the meter into the circuit.
However, it is frequently desirable to measure the DC current in a conductor without having to break the circuit and thereby temporarily interrupt current flow. In many applications, breaking the circuit is difficult. For example, breaking the circuit may involve cutting and splicing a wire. In many applications, breaking the circuit is undesirable because it will interrupt the operation of an electrical device.
As a result, there is a need for a current measurement device that does not require breaking of the circuit for which current is being measured. In response to this need, the prior art has provided Hall effect current sensors. Hall effect current sensors produce a voltage that is proportional to a magnetic field within which the sensor is disposed, according to well known principles. Since the magnetic field surrounding a conductor is proportional to the amount of current flowing therethrough, a Hall effect current sensor indirectly measures the amount of current in the conductor.
Although Hall effect current sensors have proven generally suitable for their intended use, Hall effect current sensors do suffer from inherent disadvantages that tend to detract from their overall desirability. For example, Hall effect current sensors require the use of a precise DC excitation source. As those skilled in the art will appreciate, the use of a precise DC excitation source has substantial disadvantages. The excitation source undesirably adds weight and bulk to the current measuring system, making its use undesirable for spacecraft and many other applications. The excitation source must also be calibrated to assure that it is operating properly. Additionally, precise DC excitation sources tend to be costly.
Thus, there exists a need in the art for a DC current measurement device that does not require breaking of the circuit and which further does not required the use of a precise DC excitation source, such as that required by contemporary Hall effect current sensors.